Roller unit and rotary compressor

ABSTRACT

A roller unit used for a rotary compressor is cylindrically formed to rotate eccentrically around a rotary shaft. The roller unit is divided into at least three rollers in an axial direction of the rotary shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-174951, filed Sep. 12, 2017, the entire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a roller unit and a rotary compressor.

BACKGROUND

A rotary compressor used, for example, for an air conditioner has a crank attached to a distal end of a rotary shaft. The crank is arranged in a centrum of a cylindrical roller and fitted to the roller. The roller is arranged in a cylinder chamber that is the centrum of a cylindrical cylinder. An outer peripheral surface of the roller abuts a distal end portion of a blade that extends from an outer peripheral side of the cylinder towards the cylinder chamber in a radial direction of the cylinder. Here, the abutment indicates a state in which the distal end portion of the blade linearly abuts the outer peripheral surface of the roller in a central axis direction of the roller. The blade abutting the outer peripheral surface of the roller functions as a partition wall that partitions the cylinder chamber into a suction chamber and a compression chamber.

When the rotary shaft is rotated by a rotation of a motor, the crank and the roller rotate eccentrically in the cylinder chamber by the rotation of the rotary shaft. By the eccentric rotation of the roller, a volume of the compression chamber and a volume of the suction chamber formed inside the cylinder chamber are changed, and a gas coolant inside the compression chamber is compressed. Here, the outer peripheral surface of the roller slides against the distal end portion of the blade in a state where the distal end portion of the blade receives a particularly large load and moment by a pressure difference between the suction chamber and the compression chamber.

Poor lubrication between the distal end portion of the blade and the outer peripheral surface of the roller may increase friction between the distal end portion and the outer peripheral surface, and may cause damage on the surfaces, which would be a cause of degraded performance and reliability of the rotary compressor. Therefore, it is necessary to secure a favorable lubrication state between the distal end portion and the outer peripheral surface (for example, see publications of Japanese Patent No. 5018829 and Japanese Patent No. 6133185).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall structural diagram of an air conditioner according to a present embodiment.

FIG. 2A is a top view of a compression mechanism part.

FIG. 2B is a perspective view of the compression mechanism part shown in FIG. 2A.

FIG. 3A is a perspective view of a blade and a roller unit of the present embodiment.

FIG. 3B is a side view of the blade and the roller unit shown in FIG. 3A and a crank portion of when a one-sided contact has occurred.

FIG. 4A is a diagram of a first reference example of the present embodiment, and shows a distribution of an oil film pressure of a lubricant that occurs between an inner peripheral surface of a roller and an outer peripheral surface of the crank portion.

FIG. 4B is a diagram of the first reference example of the present embodiment, and shows a distribution of an oil film pressure of a lubricant that occurs between each inner peripheral surface of two rollers and the outer peripheral surface of the crank portion.

FIG. 4C shows a distribution of an oil film pressure of a lubricant that occurs between each inner peripheral surface of first, second, and third rollers and the outer peripheral surface of the crank portion of the present embodiment.

FIG. 5A is an example of a groove that is arranged on a side surface of each roller of the roller unit.

FIG. 5B is an example of a groove that is arranged on the side surface of each roller of the roller unit.

FIG. 5C is an example of a groove that is arranged on the side surface of each roller of the roller unit.

FIG. 6A is a perspective view of a blade and a roller unit as a second reference example of the present embodiment.

FIG. 6B is a side view of the blade and the roller unit shown in FIG. 6A and a crank portion of when a one-sided contact has occurred.

FIG. 7A is a diagram showing a first modified example of the present embodiment, and explaining a relationship of each width of four rollers of a roller unit.

FIG. 7B is a diagram showing a second modified example of the present embodiment, and explaining a relationship of each width of five rollers of a roller unit.

DETAILED DESCRIPTION

A roller unit used for a rotary compressor of an embodiment is cylindrically formed to rotate eccentrically around a rotary shaft, and is divided into at least three rollers in an axial direction of the rotary shaft.

A rotary compressor of the embodiment comprises an electric motor part, a compression mechanism part that is driven by the electric motor part, and a sealed casing that accommodates the electric motor part and the compression mechanism part, wherein the electric motor part comprises a motor rotor that is rotary driven, and a rotary shaft that is rotated by the rotary drive of the motor rotor, and the compression mechanism part comprises a cylinder that has a cylinder chamber, a roller unit that is arranged in the cylinder chamber in a state of being fitted to the rotary shaft, that is cylindrically formed to rotate eccentrically in the cylinder chamber along with an eccentric rotation of the rotary shaft, and that is divided into at least three rollers in an axial direction of the rotary shaft, and a blade that is pushed in a direction abutting an outer peripheral surface of the roller unit, has a distal end portion that abuts the outer peripheral surface by being pushing, and partitions the cylinder chamber into a suction chamber and a compression chamber in a state where the distal end portion abuts the outer peripheral surface.

Hereinafter, an embodiment will be explained with reference to the accompanying drawings. In some of the drawings, illustrations of some members are omitted for clarification of the illustration.

An air conditioner 10 of the present embodiment shown in FIG. 1 is, for example, used for an air conditioner. The air conditioner 10 comprises a rotational rotary compressor 20 that comprises a compressor main body 30 and an unillustrated accumulator and compresses a gas coolant that is a working fluid, and a condenser 81 that condenses a high-pressure gas coolant compressed by the rotary compressor 20 and changes it to a liquid coolant. The air conditioner 10 comprises an expansion device 83 that is connected to the condenser 81 and reduces pressure of, and adiabatically expands, the liquid coolant, and an evaporator 85 that is arranged between the expansion device 83 and the accumulator and that evaporates the liquid coolant to change the liquid coolant into the gas coolant. In the air conditioner 10, the coolant circulates while changing phases between the gas coolant and the liquid coolant. In the process of circulation, heat dissipation and heat absorption are performed, and space heating, space cooling, heating, and cooling are performed by the heat dissipation and the heat absorption.

The compressor main body 30 of the rotary compressor 20 comprises a discharge pipe 31, a suction pipe 33, an electric motor part 40, a compression mechanism part 50 that is driven by the electric motor part 40, and a sealed cylindrical casing 70 that accommodates the electric motor part 40 and the compression mechanism part 50.

The discharge pipe 31 is attached to an upper surface (upper part) of the casing 70, and is connected to the condenser 81. The discharge pipe 31 discharges a high-pressure gas coolant compressed by the compressor main body 30 towards the condenser 81.

The suction pipe 33 is connected to an unillustrated accumulator and the compressor main body 30. The suction pipe 33 leads the gas coolant changed by the evaporator 85 from the evaporator 85 to the compressor main body 30 through the accumulator.

Inside the casing 70, the electric motor part 40 is arranged in the upper part of the casing 70, and the compression mechanism part 50 is arranged in a lower part of the casing 70. The compression mechanism part 50 is immersed in a lubricant 91 that is stored at the inner bottom part of the casing 70. The water surface of the lubricant 91 is positioned lower than the electric motor part 40, and higher than a hereinafter described cylinder 51 of the compression mechanism part 50.

The electric motor part 40 comprises a motor stator 41 that is attached on the inside of the casing 70, a rotary driven motor rotor 43 whose position is fixed by the motor stator 41, and a cylindrical rotary shaft 45 that is connected to the motor rotor 43 and rotates anti-clockwise by the rotary drive of the motor rotor 43.

The motor stator 41 is cylindrical, and the motor rotor 43 is arranged in the centrum of the motor stator 41. For example, the motor stator 41 includes a coil for supplying electricity, and the motor rotor 43 includes a permanent magnet.

The rotary shaft 45 is arranged on a central axis C of the motor rotor 43, and extends from the upper part of the casing 70 to the compression mechanism part 50 at the lower part of the casing 70. As shown in FIG. 2B, the cylindrical rotary shaft 45 comprises a main body part (axis portion) of the rotary shaft 45 provided on the rotary shaft 45, a centrum 45 a arranged along the entire length of the main body part of the rotary shaft 45, and a crank portion 47 attached to the distal end of the main body part of the rotary shaft 45. The crank portion 47 is rotated eccentrically with respect to the central axis C by the rotation of the main body part of the rotary shaft 45.

In a state of being positioned and fixed on the inner peripheral surface of the casing 70, the compression mechanism part 50 is coupled to the motor rotor 43 of the electric motor part 40 through the crank portion 47 and the rotary shaft 45. The compression mechanism part 50 comprises a cylindrical cylinder 51 comprising a cylinder chamber 51 a, a pair of first and second cylindrical bearings 53 a and 53 b arranged on the upper surface and lower surface of the cylinder 51, and a cylindrical roller unit 55 arranged on the cylinder chamber 51 a in a state of being fitted to the crank portion 47.

As shown in FIG. 2A and FIG. 2B, the cylinder chamber 51 a indicates a centrum of the cylindrical cylinder 51.

As shown in FIG. 1, the rotary shaft 45 is inserted through the first bearing 53 a and is rotatably supported by the first bearing 53 a. The rotary shaft 45 is inserted through the roller unit 55 and into the second bearing 53 b, and is rotatably supported by the second bearing 53 b.

As shown in FIG. 2A and FIG. 2B, along with the eccentric rotation of the crank portion 47, the roller unit 55 rotates eccentrically inside the cylinder chamber 51 a while a part of its outer peripheral surface of the roller unit 55 comes in contact along the inner peripheral surface of the cylinder 51. A detailed configuration of the roller unit 55 will be explained later on.

The compression mechanism part 50 comprises a blade slot 59 that is arranged on the cylinder 51, a blade 61 that is arranged inside the blade slot 59, and a pushing member 63 that pushes the blade 61. For illustration clarification, in FIG. 2B, the illustration of the pushing member 63 is omitted.

The blade slot 59 is a gap for communicating the cylinder chamber 51 a with the outside of the cylinder 51 in a radial direction of the cylinder 51. The blade slot 59 is arranged linearly.

The blade 61 is pushed by the pushing member 63 in a direction that abuts the outer peripheral surface of the roller unit 55. The blade 61 comprises a distal end portion 61 a that abuts the outer peripheral surface when being pushed. Here, to abut indicates that the distal end portion 61 a of the blade 61 is pushed towards the outer peripheral surface of the roller unit 55 in a radial direction of the roller unit 55. It is preferable to perform the abutting, for example, linearly in the central axis C direction of the roller unit 55 (see FIG. 3A). By a push of the pushing member 63 and a push back from the eccentrically rotating roller unit 55, the blade 61 is movable in the radial direction of the roller unit 55 between the cylinder chamber 51 a of the cylinder 51 and the outside of the cylinder 51.

In a state where the distal end portion 61 a abuts the outer peripheral surface of the roller unit 55, the blade 61 functions as a partition wall that partitions the cylinder chamber 51 a into a suction chamber 51 b that is connected to the suction pipe 33 and suctions a gas coolant from the suction pipe 33, and a compression chamber 51 c that compresses the coolant. For illustration clarification, in FIG. 2B, the illustration of the suction pipe 33 is omitted. The suction chamber 51 b and the compression chamber 51 c are spaces partitioned into the inner peripheral surface of the cylinder 51 and the outer peripheral surface of the roller unit 55 by the blade 61. The compression chamber 51 c is a different space from the suction chamber 51 b. Depending on the eccentric rotation of the roller unit 55, the volume changes in each of the suction chamber 51 b and the compression chamber 51 c formed in the cylinder chamber 51 a.

The pushing member 63 has a spring member that pushes the blade 61 towards the roller unit 55.

A configuration of the roller unit 55 will be explained with reference to FIG. 3A and FIG. 3b . For illustration clarification, illustrations of the crank portion 47 and the rotary shaft 45 are omitted in FIG. 3A, and an illustration of the rotary shaft 45 is omitted in FIG. 3B.

The roller unit 55 comprises first and second cylindrical rollers (hereinafter, referred to as rollers 55 a, 55 b, respectively) arranged on both ends of the roller unit 55 in the central axis C direction of the roller unit 55, and a cylindrical third roller (hereinafter, referred to as a roller 55 c) sandwiched between the roller 55 a and the roller 55 b in the central axis C direction of the roller unit 55. Here, the roller sandwiched between the roller 55 a and the roller 55 b is only the roller 55 c. However, other cases may also be considered. In the manner shown in FIG. 7A and FIG. 7B, at least one sandwiched roller should be arranged. Therefore, the roller unit 55 should be divided into at least three rollers in the central axis C direction of the roller unit 55 (rotary shaft 45).

In the central axis C direction of the roller unit 55 (rotary shaft 45), the roller 55 a is adjacent to the roller 55 c, and the roller 55 c is adjacent to the roller 55 b. One of the two side surfaces of the roller 55 a faces one of the two side surfaces of the roller 55 c. In the same manner, the other side surface of the roller 55 c faces one of the two side surfaces of the roller 55 b. In the central axis C direction of the roller unit 55, the rollers 55 a, 55 c, and 55 b may be arranged slightly apart from each other with a gap therebetween. In the central axis C direction of the roller unit 55, the rollers 55 a, 55 c, and 55 b may be adjacent to and laminated with each other. Each of the rollers 55 a, 55 b, and 55 c are made independently rotatable with respect to the rotary shaft 45 (crank portion 47). The inner diameter of each of the rollers 55 a, 55 b, and 55 c is the same with respect to each other, and the outer diameter of each of the rollers 55 a, 55 b, and 55 c is the same with respect to each other. The outer peripheral surface and the inner peripheral surface of each of the rollers 55 a, 55 b, and 55 c are smooth without any unevenness.

The inner diameter of each of the rollers 55 a, 55 b, and 55 c is approximately the same as the outer diameter of the crank portion 47. However, there is a slight clearance between the inner peripheral surface of the rollers 55 a, 55 b, and 55 c and the outer peripheral surface of the crank portion 47, and a lubricant is introduced in the clearance in the manner mentioned later on. The crank portion 47 is inserted inside each of the rollers 55 a, 55 b, and 55 c and is fitted thereto. In the state where the crank portion 47 is fitted to the rollers 55 a, 55 b, and 55 c, the outer peripheral surface of each of the rollers 55 a, 55 b, and 55 c is arranged approximately on a same plane.

In the present embodiment, an unillustrated lubricant that has a thickness of several μm is present between the outer peripheral surface of the crank portion 47 and the inner peripheral surface of each of the rollers 55 a, 55 b, and 55 c. The outer peripheral surface of the crank portion 47 is abuttable against the inner peripheral surface of each of the rollers 55 a, 55 b, and 55 c through the lubricant. Under the fluid lubrication through the lubricant, the rollers 55 a, 55 b, and 55 c rotate eccentrically together with the crank portion 47.

The outer peripheral surface of each of the rollers 55 a, 55 b, and 55 c is abuttable against the distal end portion 61 a of the blade 61.

If the rotary compressor 20 increases in size and speed, a runout of the rotary shaft 45 may increase. In such case, as shown in FIG. 3B, the rollers 55 a, 55 b, and 55 c attached to the rotary shaft 45 through the crank portion 47 will come to be in a tilted state against the distal end portion 61 a of the blade 61. For example, the roller 55 a arranged on an end portion of the roller unit 55 abuts point-like only against a part of the distal end portion 61 a of the blade 61, that is, would be subject to a one-sided contact. When the one-sided contact occurs, for example, the one-sided contact causes the roller 55 a to be displaced (moved) in the manner indicated by arrow A of FIG. 3B in a radial direction of the roller 55 a by a several μm, which is a thickness of the lubricant (oil film) between the crank portion 47 and the roller 55 a.

The displacement herein will be explained. As shown in FIG. 3B, a case in which a one-sided contact portion 65 has occurred by the distal end portion 61 a of the blade 61 causing a one-sided contact to occur at the roller 55 a will be considered. The displacement occurs by the blade 61 pushing the one-sided contact portion 65 in the radial direction of the roller 55 a, and the one-sided contact portion 65 moving close to the outer peripheral surface of the crank portion 47 in the manner indicated by arrow A in FIG. 3B. Specifically, the roller 55 a is moved in the radial direction of the roller 55 a by being pushed to an opposite side of the blade 61 by the distal end portion 61 a of the blade 61. The roller 55 a moves in the radial direction of the roller 55 a with respect to the rollers 55 b and 55 c.

Here, the one-sided contact portion 65 was used for the explanation. However, the same displacement may also be performed for the roller 55 b to which a one-sided contact has occurred. Furthermore, the same displacement may also be performed for a sliding surface that is a contact surface between the distal end portion 61 a of the blade 61 and the outer peripheral surface of each of the rollers 55 a, 55 b, and 55 c. The sliding surface includes the contact surface between the distal end portion 61 a of the blade 61 and the outer peripheral surface of each of the rollers 55 a, 55 b, and 55 c that are arranged in parallel with respect to each other. Since the one-sided contact does not occur for the roller 55 c, the roller 55 c possesses a desired large oil film load capability.

Here, a rotary compressor of the air conditioner of a first reference example will be explained for comparison with the present embodiment. In this first reference example, a roller unit 55 is assumed as having a roller 155 a attached to a crank portion 47 in the manner shown in FIG. 4A. Alternatively, in the first reference example, the roller unit 55 is assumed as having two rollers 155 a and 155 b attached to the crank portion 47 in the manner shown in FIG. 4B. FIG. 4A shows an oil film pressure distribution 167 a of a lubricant occurring between an inner peripheral surface of a roller 155 a and an outer peripheral surface of the crank portion 47. FIG. 4B shows oil film pressure distributions 167 a and 167 b of a lubricant occurring between the inner peripheral surface of two rollers 155 a and 155 b and the outer peripheral surface of the crank portion 47. In FIG. 4A and FIG. 4B, the length of the arrows in parabolas of the oil film pressure distributions 167 a and 167 b indicates the magnitude of the oil film pressure.

Generally, the oil film pressure increases at a central part in the central axis C direction of each of the rollers, and gradually decreases from the central part towards both ends. Furthermore, the longer the length of the roller in the central axis C direction of the roller unit 55 is, the larger the oil film pressure becomes, which would disturb the displacement of the roller. Accordingly, it is preferable that the oil film pressure is small at the roller at which the one-sided contact occurs.

In the configurations shown in FIG. 4A and FIG. 4B, the number of rollers in the roller unit 55 is small.

Therefore, the magnitude of the oil film pressure is not small enough for the oil film pressure to be minimized. Accordingly, even if the one-sided contact occurs, the rollers 155 a and 155 b would not be able to be displaced in the radial direction of the roller by the amount of thickness of the lubricant.

In the following, the rotary compressor 20 of the air conditioner 10 of the present embodiment will be explained again. In the present embodiment, as shown in FIG. 4C, adjustment is made for the oil film pressure of each of the rollers 55 a and 55 b to be minimized, and widths L1 and L2 of each of the rollers 55 a and 55 b to become narrower than a width L3 of the roller 55 c. The widths L1, L2, and L3 are calculated in advance to an optimal value in accordance with a compression condition of the rotary compressor 20. Particularly in rollers 55 a and 55 b to which the one-sided contact frequently occurs, the widths L1 and L2 are narrower than width L11 of the one roller 155 a shown in FIG. 4A, or than widths L11 and L12 of the two rollers 155 a and 155 b shown in FIG. 4B.

Here, the relationship of the widths L1, L2, and L3 will be explained. The following formula (1) may be established for the widths L1, L2, and L3. Formula (2) may also be established together with formula (1).

L3>L1 and L3>L2  (1)

L1=L2  (2)

Now, the calculation of widths L1 and L2 will be explained. Since the calculation of each of the widths L1 and L2 is equivalent to each other, here, the width L1 will be used for the explanation.

The width L1 should be equal to or greater than a minimum width calculated from Sommerfeld number S and a Gumbel boundary condition of an infinitely short bearing (minor axis width bearing).

The Sommerfeld number S is calculated by formula (3) below using a gap c between the crank portion 47 and the roller 55 a, a radius R of the crank portion 47, the number of rotations N′ of the rotary shaft 45, a viscosity η of the lubricant, and a surface pressure p between the crank portion 47 and the roller 55 a.

$\begin{matrix} {S = \frac{\eta \; N^{\prime}}{{p\left( {c\text{/}R} \right)}^{2}}} & (3) \end{matrix}$

Here, for example, the gap c/radius R is 0.001, the number of rotations N′ is 60 rps, the viscosity η is 2.8×10⁻³, and the surface pressure p is 0.375 Mpa.

The Gumbel boundary condition of an infinitely short bearing (minor axis width bearing) is calculated by formula (4) below using an eccentricity ratio ε, a diameter D of the roller 55 a, the Sommerfeld number S calculated by formula (3), and the width L1 of the roller 55 a.

$\begin{matrix} {{S\left( \frac{L\; 1}{D} \right)}^{2} = \frac{\left( {1 - ɛ^{2}} \right)^{2}}{\pi \; ɛ\sqrt{{16\; ɛ^{2}} + {\pi^{2}\left( {1 - ɛ^{2}} \right)}}}} & (4) \end{matrix}$

Here, for example, the eccentricity ratio ε is 0.9, the diameter D is 0.024 m, and the Sommerfeld number S is 0.048. A width of the roller 55 a that satisfies the above should be used.

FIG. 4C shows distributions 67 a, 67 b, and 67 c of the oil film pressure of the lubricant that occurs between the inner peripheral surface of each of the rollers 55 a, 55 b, and 55 c of the roller unit 55 and the outer peripheral surface of the crank portion 47 of the present embodiment. The adjustment and the calculation performed in the present embodiment reduce the width of the rollers 55 a and 55 b in the central axis C direction sufficiently, and minimize the oil film pressure at each of the rollers 55 a and 55 b, thereby facilitating the displacement of the rollers 55 a and 55 b.

Now, a groove 57 on the side surface of each of the rollers 55 a, 55 b, and 55 c will be explained. Since the configuration of the side surface and the groove 57 of each of the rollers is equivalent to each other, here, the roller 55 a will be used for the explanation. The side surface mentioned herein is, for example, a plane, and not the outer peripheral surface of the roller 55 a to which the blade 61 abuts, and includes a first facing surface of the roller 55 a that faces the roller 55 c and a second facing surface of the roller 55 a that faces the first facing surface.

As shown in FIG. 5A, FIG. 5B, and FIG. 5C, the roller 55 a comprises a plurality of radial grooves 57 arranged at least on one of the two side surfaces. In the present embodiment, one of the grooves 57 shown in FIG. 5A, FIG. 5B, and FIG. 5C can be selected and adopted for the roller 55 a. Similarly, one of the grooves 57 shown in FIG. 5A, FIG. 5B, and FIG. 5C can be selected and adopted for the rollers 55 b and 55 c. Different structures of the grooves may be adopted as appropriate for each of the rollers 55 a, 55 b, and 55 c, for example, by adopting the structure of FIG. 5A or FIG. 5B for the roller 55 a, and adopting the structure of FIG. 5C for the rollers 55 b and 55 c.

The grooves 57 are preferably arranged on the side surface of the roller 55 a to which side the roller 55 c is adjacent. The grooves 57 extend radially from the rotary shaft 45 towards a sliding surface (the outer peripheral surface of the roller 55 a). When, for example, a one-sided contact occurs, a difference occurs in the rotation speed of each of the rollers 55 a, 55 b, and 55 c. The rotation speed difference between each of the rollers 55 a, 55 b, and 55 c with grooves 57 causes an inflow of the lubricant from the centrum of the roller 55 a to the sliding surface to improve. This lubricant is present between the outer peripheral surface of the crank portion 47 and the inner peripheral surface of each of the rollers 55 a, 55 b, and 55 c. The grooves 57 are arranged along a direction in which the lubricant is pushed out by the rotation of the roller 55 a towards the outer peripheral direction of the roller 55 a. The grooves 57 are, for example, arranged rotationally symmetric to the central axis C.

As shown in FIG. 5A, the grooves 57 may communicate with the centrum of the roller 55 a, but do not have to communicate with the outer peripheral surface of the roller 55 a.

As shown in FIG. 5B, the grooves 57 may communicate with the centrum of the roller 55 a and the outer peripheral surface of the roller 55 a. In this case, it is preferred that the grooves 57 are narrow.

Now, with reference to FIG. 5C, a right side surface of the roller 55 a and a left side surface of the roller 55 c that faces this right side surface will be explained. In FIG. 5C, the roller 55 a and the roller 55 c are disassembled and shown side-by-side for comparison. On the right side surface, the grooves 57 of the roller 55 a may communicate with the centrum of the roller 55 a while not communicating with the outer peripheral surface of the roller 55 a. On the left side surface, the grooves 57 of the roller 55 c may communicate with the outer peripheral surface of the roller 55 c while not communicating with the centrum of the roller 55 c. The grooves 57 are arranged on the two side surfaces adjacent to (facing) each other.

The operation of the present embodiment will be explained below.

When the motor rotor 43 is rotated, the rotary shaft 45 is rotated. Then, the crank portion 47 attached to the rotary shaft 45 is rotated eccentrically. The roller unit 55 rotates eccentrically by the eccentric rotation of the crank portion 47. The blade 61 is pushed towards the outer peripheral surface of the roller unit 55 by the pushing member 63, and the distal end portion 61 a of the blade 61 abuts the outer peripheral surface of the roller unit 55.

While a part of the outer peripheral surface of the roller unit 55 comes in contact along the inner peripheral surface of the cylinder 51, the roller unit 55 rotates eccentrically inside the cylinder chamber 51 a. By the eccentric rotation of the roller unit 55, a low-pressure gas coolant is suctioned into suction chamber 51 b in the cylinder chamber 51 a from the suction pipe 33. Here, the lubricant 91 flows into the suction chamber 51 b through the suction pipe 33 or the centrum 45 a. By further eccentric rotation of the roller unit 55, the gas coolant including the lubricant 91 moves from the suction chamber 51 b to the compression chamber 51 c, which causes the volume of the compression chamber 51 c to gradually decrease. The decrease in the volume of the compression chamber 51 c causes the gas coolant to be compressed in the compression chamber 51 c. A further eccentric rotation of the roller unit 55 causes the volume of the compression chamber 51 c to further decrease, thereby further compressing the gas coolant in the compression chamber 51 c so that the pressure of the gas coolant reaches a desired pressure. Then, the high-pressure gas coolant is discharged to the centrum 45 a of the rotary shaft 45 from a discharge hole 51 d (see FIG. 2A) that communicates with the compression chamber 51 c. This high-pressure gas coolant fills an upper end portion inside the casing 70 that is positioned above the electric motor part 40 from the centrum 45 a of the rotary shaft 45, and is discharged from the discharge pipe 31. The discharged gas coolant is condensed at the condenser 81 and changes into a liquid coolant. The liquid coolant is depressurized and adiabatically expanded by the expansion device 83, then is evaporated by the evaporator 85 and changed into a gas coolant. In the evaporator 85, evaporative latent heat is deprived from the surrounding air, allowing a space cooling operation to be exhibited. The gas coolant is suctioned again from the evaporator 85 to the suction chamber 51 b through the accumulator and the suction pipe 33. In the case where the rotary compressor 20 is mounted on a refrigerator, etc., a freezing operation and a cooling operation can be exhibited.

Here, for comparison with the present embodiment, a second reference example will be explained. In the second reference example, as shown in FIG. 6A and FIG. 6B, a roller unit 55 has only one roller 155 a attached to a rotary shaft 45 through a crank portion 47. For illustration clarification, illustrations of the crank portion 47 and the rotary shaft 45 are omitted in FIG. 6A, and an illustration of the rotary shaft 45 is omitted in FIG. 6B.

If a rotary compressor 20 increases in size and speed, a runout of the rotary shaft 45 may increase. In such case, as shown in FIG. 6B, the roller 155 a will come to be in a tilted state against a distal end portion 61 a of a blade 61. The roller 155 a will then abut point-like only against a part of the distal end portion 61 a of the blade 61, that is, would be subject to a one-sided contact. Specifically, an end portion of the roller 155 a in the central axis direction of the roller 155 will come in one-sided contact with only a part of the distal end portion 61 a of the blade 61. As in the second reference example, in the case where the roller unit 55 is not divided, and only one roller 155 a is arranged, a width L11 of the roller 155 would not be adjusted. Therefore, the oil film pressure would not be minimized. Accordingly, even if the one-sided contact occurs, the roller 155 a would not be able to be displaced in the radial direction of the roller 155 a by the amount of thickness of the lubricant. Therefore, a coating on these surfaces at the one-sided contact portion would become damaged. Also, in some cases, a solid contact surface pressure between the roller 155 a and the distal end portion 61 a of the blade 61 may increase, causing the distal end portion 61 a of the blade 61 to be worn away excessively. This would be the same even when the roller unit 55 is divided in two.

The present embodiment will be explained again. Even in the present embodiment, in some cases, a runout of the rotary shaft 45 may increase. In such case, as shown in FIG. 3B, the rollers 55 a, 55 b, and 55 c attached to the rotary shaft 45 through the crank portion 47 will come to be in a tilted state against the distal end portion 61 a of the blade 61. The roller 55 a that is an end portion of the roller unit 55 would then abut point-like only against part of the distal end portion 61 a of the blade 61, that is, would be subject to a one-sided contact. When the one-sided contact occurs, for example, the solid contact surface pressure between the roller 55 a and the distal end portion 61 a of the blade 61 may increase.

However, in the present embodiment, since the roller unit 55 is divided into the three rollers of 55 a, 55 b, and 55 c, the roller 55 a subjected to the one-sided contact would be displaced by the one-sided contact in the radial direction of the roller 55 a by the amount of oil film. Specifically, the roller 55 a is moved in the radial direction of the roller 55 a by being pushed to an opposite side of the blade 61 by the distal end portion 61 a of the blade 61. Such displacement (movement) will suppress the one-sided contact, reduce the solid contact surface pressure, and improve the ability of the roller 55 a to follow the displacement in the radial direction with respect to the blade 61. Here, the roller 55 a was used for the explanation. However, the same also applies to the roller 55 b.

Furthermore, the widths L1, L2, and L3 of each of the rollers 55 a, 55 b, and 55 c are adjusted by the above-mentioned formulas (1) and (2), and are calculated in advance by the above-mentioned formulas (3) and (4). Thereby, the oil film pressure in each of the rollers 55 a and 55 b becomes minimized, and the displacement would be readily performed. By adjusting the width L3, a width that is equal to or longer than a predetermined width in the central axis C direction would be secured for the roller 55 c. Thereby, the roller 55 c would possess a desirable large oil film load capability. Therefore, excessive friction may be prevented from occurring between the roller 55 c and the distal end portion 61 a of the blade 61.

By dividing the roller unit 55 into the three rollers of 55 a, 55 b, and 55 c, the increasing solid contact surface pressure between the roller unit 55 and the distal end portion 61 a of the blade 61 would be reduced. Furthermore, by dividing the roller unit 55 into the three rollers of 55 a, 55 b, and 55 c, the lubricant would be smoothly supplied from the gap between each of the rollers 55 a, 55 b, and 55 c in the central axis C direction of the roller unit 55 to the sliding surface. Here, the sliding surface includes the one-sided contact portion 65, a contact portion between the distal end portion 61 a of the blade 61 and the outer peripheral surface of each of the rollers 55 a, 55 b, and 55 c that have come in contact by the displacement, and a contact surface between the distal end portion 61 a of the blade 61 and the outer peripheral surface of each of the rollers 55 a, 55 b, and 55 c that are arranged in parallel with respect to each other. In the present embodiment, the grooves 57 improve the ability of the lubricant to be supplied to the sliding surface.

According to the present embodiment, the roller unit 55 used for the rotary compressor 20 is cylindrically formed to rotate eccentrically around the rotary shaft 45 in the cylinder chamber 51 a of the cylinder 51 arranged in a compression mechanism part 50, has an outer peripheral surface that abuts the blade 61 that partitions the cylinder chamber 51 a into the suction chamber 51 b and the compression chamber 51 c, and is divided into at least three rollers 55 a, 55 b, and 55 c in an axial direction of the rotary shaft 45.

According to such configuration, even if the one-sided contact occurs, by the one-sided contact, the roller subjected to the one-sided contact can be displaced in the radial direction of the roller by the amount of the oil film. Therefore, the roller unit 55 that is capable of reducing the solid contact surface pressure increased by the one-sided contact can be provided. A favorable lubrication state would be secured at the roller unit 55 and the distal end portion 61 a of the blade 61, which would prevent the excessive friction from occurring between the roller unit 55 and the distal end portion 61 a of the blade 61. Furthermore, the coating on these surfaces can be prevented from being damaged, which would secure high performance and high reliability of the roller unit 55.

The present embodiment does not divide the roller unit 55 into two rollers 155 a and 155 b. According to the present embodiment, the at least three rollers 55 a, 55 b, and 55 c include the first roller 55 a and the second roller 55 b that are arranged on both ends of the roller unit 55 in the axial direction, and the third roller 55 c that is sandwiched between the first roller 55 a and the second rollers 55 b in the central axis direction. When the width of each of the first roller 55 a, the second roller 55 b, and the third roller 55 c in the axial direction is L1, L2, and L3, formula (1) such as L3>L1 and L3>L2 may be established. Furthermore, formula (2) such as L1=L2 may be established. The widths L1 and L2 should be equal to or greater than a minimum width calculated from a Sommerfeld number and a Gumbel boundary condition of an infinitely short bearing. This allows the oil film pressure at each of the rollers 55 a and 55 b to be minimized, allows the displacement to be performed with certainty, and allows the ability of the roller 55 a to follow the displacement in the radial direction of the roller 55 a with respect to the blade 61.

In the present embodiment, at least one roller 55 a of the at least three rollers 55 a, 55 b, and 55 c has a plurality of grooves 57 extending radially from the rotary shaft 45 on a side surface adjacent to another roller 55 c of the at least three rollers 55 a, 55 b, and 55 c. The rotation speed difference between each of the rollers 55 a, 55 b, and 55 c possessing the grooves 57 allows the lubricant to flow into the sliding surface. Therefore, a favorable lubrication state would be secured at the sliding surface, which would prevent the excessive friction from occurring between the roller unit 55 and the distal end portion 61 a of the blade 61, and would prevent the coating on these surfaces from being damaged.

In the present embodiment, the grooves 57 are arranged along a direction in which the lubricant is pushed out towards the outer peripheral direction of the roller 55 a by the rotation of the roller 55 a. Therefore, the lubricant can be supplied towards the sliding surface without any waste.

In the present embodiment, the grooves 57 communicate with the centrum of the cylindrical roller 55 a, however, do not communicate with the outer peripheral surface of the roller 55 a. That is, in FIG. 5A, the lubricant is supplied to the sliding surface through the side surface of the roller 55 a. In this manner, the lubricant can be supplied to the sliding surface from the centrum of the roller 55 a through the grooves 57 and the side surface of the roller 55 a. Furthermore, the grooves 57 do not communicate with the outer peripheral surface. Therefore, the gas coolant compressed at the compression chamber 51 c can be prevented from leaking to the centrum of the roller 55 a from the compression chamber 51 c through the grooves 57.

In the present embodiment, the grooves 57 communicate with the centrum of the cylindrical roller 55 a, and with the outer peripheral surface of the roller 55 a. That is, in FIG. 5B, the lubricant is supplied to the sliding surface through the grooves 57. Therefore, the lubricant can be supplied directly to the sliding surface through the grooves 57. If the grooves 57, for example, are made sufficiently narrow, the gas coolant can be prevented from being reversed from the compression chamber 51 c to the centrum of the roller 55 a.

In the present embodiment, on the side surface of one roller 55 a of at least three rollers 55 a, 55 b, and 55 c, the grooves 57 communicate with the centrum of the cylindrical roller 55 a, however, do not communicate with the outer peripheral surface of the roller 55 a. Furthermore, on the side surface of another roller 55 c adjacent to the side surface of the roller 55 a, the grooves 57 communicate with the outer peripheral surface of the other roller 55 c without communicating with the centrum of the other cylindrical roller 55 c. In FIG. 5C, depending on the speed difference of the rollers 55 a and 55 c, the grooves 57 of the roller 55 a may communicate with the groove 57 of the roller 55 c, or may have the communication disconnected and blocked. Therefore, the lubricant will be supplied intermittently, which would be effective in the case of such usage.

According to the present embodiment, the rotary compressor 20 comprises the electric motor part 40, the compression mechanism part 50 that is driven by the electric motor part 40, and the sealed casing 70 that accommodates the electric motor part 40 and the compression mechanism part 50. The electric motor part 40 comprises the motor rotor 43 that is rotary driven, and the rotary shaft 45 that rotates by the rotary drive of the motor rotor 43. The compression mechanism part 50 comprises the cylinder 51 comprising the cylinder chamber 51 a, the roller unit 55 mentioned above that is arranged in the cylinder chamber 51 a in a state of being fitted to the rotary shaft 45 and that rotates eccentrically in the cylinder chamber 51 a along with the eccentric rotation of the rotary shaft 45, and the blade 61 that is pushed in a direction that abuts the outer peripheral surface of the roller unit 55, comprises the distal end portion 61 a that abuts the outer peripheral surface by pushing, and partitions the cylinder chamber 51 a into the suction chamber 51 b and the compression chamber 51 c in a state where the distal end portion 61 a abuts the outer peripheral surface.

According to such configuration, even if the one-sided contact occurs, by the one-sided contact, the roller subjected to the one-sided contact can be displaced in the radial direction of the roller by the amount of the oil film. Therefore, the rotary compressor 20 that is capable of reducing the solid contact surface pressure increased by the one-sided contact can be provided. A favorable lubrication state can be secured at the roller unit 55 and the distal end portion 61 a of the blade 61, which would prevent the excessive friction from occurring between the roller unit 55 and the distal end portion 61 a of the blade 61. Furthermore, the coating on these surfaces can be prevented from being damaged, which would secure high performance and high reliability of the rotary compressor 20.

FIG. 7A shows a first modified example of the present embodiment. As shown in FIG. 7A, a roller unit 55 may comprise four rollers 55 a, 55 b, 55 c, and 55 d, or may be divided in four in the central axis C direction of the roller unit 55. Here, third and fourth rollers 55 c and 55 d are sandwiched between the roller 55 a and the roller 55 b.

The relationship of widths L1, L2, L3, and L4 of each of the rollers 55 a, 55 b, 55 c, and 55 d will be explained. The following formula (5) may be established for the widths L1, L2, L3, and L4.

L3+L4>L1 and L3+L4>L2  (5)

Formula (2) mentioned above may also be established together with formula (5).

FIG. 7B shows a second modified example of the present embodiment. As shown in FIG. 7B, the roller unit 55 may comprise five rollers 55 a, 55 b, 55 c, 55 d, and 55 e, or may be divided in five in the central axis C direction of the roller unit 55. Here, third, fourth, and fifth rollers 55 c, 55 d, and 55 e are sandwiched between the roller 55 a and the roller 55 b.

The relationship of widths L1, L2, L3, L4, and L5 of each of the rollers 55 a, 55 b, 55 c, 55 d, and 55 e will be explained. The following formula (6) may be established for the widths L1, L2, L3, L4, and L5.

L3+L4+L5>L1 and L3+L4+L5>L2  (6)

Formula (2) mentioned above may also be established together with formula (6).

Here, the sum of the widths of each of N rollers sandwiched between the roller 55 a and the roller 55 b is SL, and N is at least one. In this case, the following formula (7) is established.

SL>L1 and SL>L2  (7)

Formula (2) mentioned above may also be established together with formula (7).

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the embodiments. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. Furthermore, it is of course also possible to realize an embodiment by combining the above-mentioned embodiments and the first and the second modified examples as appropriate. 

What is claimed is:
 1. A roller unit used for a rotary compressor, is cylindrically formed to rotate eccentrically around a rotary shaft, wherein the roller unit is divided into at least three rollers in an axial direction of the rotary shaft.
 2. The roller unit according to claim 1, wherein the at least three rollers comprise: a first roller and a second roller arranged on both ends in the axial direction; and a third roller sandwiched between the first roller and the second roller in the axial direction, and when widths of each of the first roller, the second roller, and the third roller in the axial direction are L1, L2, and L3, L3>L1 and L3>L2 are satisfied.
 3. The roller unit according to claim 2, wherein L1=L2 is satisfied.
 4. The roller unit according to claim 3, wherein the widths L1 and L2 of each of the first roller and the second roller are equal to or greater than a minimum width calculated from a Sommerfeld number and a Gumbel boundary condition of an infinitely short bearing.
 5. The roller unit according to claim 1, wherein at least one roller of the at least three rollers has a plurality of grooves that are arranged on a side surface adjacent to another roller of the at least three rollers and that extend radially from the rotary shaft.
 6. The roller unit according to claim 5, wherein the plurality of grooves are arranged along a direction in which a lubricant is pushed out towards an outer peripheral direction of the roller by a rotation of the roller.
 7. The roller unit according to claim 5, wherein the plurality of grooves communicate with a centrum of the cylindrical roller, and do not communicate with an outer peripheral surface of the roller.
 8. The roller unit according to claim 5, wherein the plurality of grooves communicate with a centrum of the cylindrical roller, and communicate with an outer peripheral surface of the roller.
 9. The roller unit according to claim 5, wherein on the side surface of one roller of the at least three rollers, the plurality of grooves communicate with a centrum of the cylindrical roller, and do not communicate with an outer peripheral surface of the roller, and on the side surface of another roller adjacent to the side surface of the one roller, the plurality of grooves communicate with an outer peripheral surface of the another roller, without communicating with a centrum of the another cylindrical roller.
 10. A rotary compressor comprising: an electric motor part; a compression mechanism part that is driven by the electric motor part; and a sealed casing that accommodates the electric motor part and the compression mechanism part, wherein the electric motor part comprises: a motor rotor that is rotary driven; and a rotary shaft that is rotated by the rotary drive of the motor rotor, and the compression mechanism part comprises: a cylinder comprising a cylinder chamber; a roller unit that is arranged in the cylinder chamber in a state of being fitted to the rotary shaft, that is cylindrically formed to rotate eccentrically in the cylinder chamber along with an eccentric rotation of the rotary shaft, and that is divided into at least three rollers in an axial direction of the rotary shaft; and a blade that is pushed in a direction that abuts an outer peripheral surface of the roller unit, comprises a distal end portion that abuts the outer peripheral surface by being pushed, and partitions the cylinder chamber into a suction chamber and a compression chamber in a state where the distal end portion abuts the outer peripheral surface.
 11. The rotary compressor according to claim 10, wherein the at least three rollers comprise: a first roller and a second roller that are arranged on both ends in the axial direction; and a third roller sandwiched between the first roller and the second roller in the axial direction, wherein when widths of each of the first roller, the second roller, and the third roller in the axial direction are L1, L2, and L3, L3>L1 and L3>L2 are satisfied.
 12. The rotary compressor according to claim 11, wherein L1=L2 is satisfied.
 13. The rotary compressor according to claim 12, wherein the widths L1 and L2 of each of the first roller and the second roller are equal to or greater than a minimum width calculated from a Sommerfeld number and a Gumbel boundary condition of an infinitely short bearing.
 14. The rotary compressor according to claim 10, wherein at least one roller of the at least three rollers has a plurality of grooves that are arranged on a side surface adjacent to another roller of the at least three rollers, and that extend radially from the rotary shaft.
 15. The rotary compressor according to claim 14, wherein the plurality of grooves are arranged along a direction in which a lubricant is pushed out towards an outer peripheral direction of the roller by a rotation of the roller.
 16. The rotary compressor according to claim 14, wherein the plurality of grooves communicate with a centrum of the cylindrical roller, and do not communicate with an outer peripheral surface of the roller.
 17. The rotary compressor according to claim 14, wherein the plurality of grooves communicate with a centrum of the cylindrical roller and an outer peripheral surface of the roller.
 18. The rotary compressor according to claim 14, wherein on the side surface of one roller of the at least three rollers, the plurality of grooves communicate with a centrum of the cylindrical roller, and do not communicate with an outer peripheral surface of the roller, and on the side surface of another roller adjacent to the side surface of the one roller, the plurality of grooves communicate with an outer peripheral surface of the another roller, without communicating with a centrum of the another cylindrical roller. 